This invention relates to the art of preparing a high by-pass protein animal feed product from partially deoiled soybeans. This high quality animal feed product is particularly suitable for feeding dairy cattle.
Since the end of World War II, soybeans have become a major agricultural commodity in the United States and in many other parts of the world. Each metric ton of soybeans typically contains around 183 kg. of oil and around 800 kg. of meal.
In "Soybean Utilization", Snyder, H. E. and Kwon, T. W., AVI Book, Van Nostrand Reinhold Company, 1987, the authors show that in the years 1980-1984 the average production of soybeans was on the order of 52 million metric tons in the United States as compared to an average world production of 85 million metric tons. World production of soybean oil for 1984/1985 was 13.3 million metric tons.
Early in 1990 (Inform, Vol. 1, No. 2 (February 1990)) it was predicted that world soybean production would increase to 107 million metric tons. The world's soybean crush was estimated to reach 88 million metric tons, showing again that a very large percentage of soybeans produced are converted into oil and meal. For the same period, soybean oil production in the United States was predicted to be 6.4 million metric tons, implying meal production of 30 million metric tons and thus a domestic soybean production of well in excess of 36.4 million metric tons.
To put the United States production in economic perspective, recent data (The Wall Street Journal, Jan. 5, 1991) listed cash prices for soybean commodities as follows:
soybeans: $5.50-1/2 bushel ($201.85/metric ton); PA1 soybean oil: $0.2083/lb ($458.26 metric ton) and PA1 soybean meal: $150 to $156/ton or $165 to $171.60/metric ton.
The production of soybean oil and meal in any given year is of vast importance to the domestic and worldwide economy as it involves many billions of dollars, worth of products. Important products include soybean oil, which is used in the United States and elsewhere throughout the world as a vegetable oil for human consumption, and soybean meal. Soybean meal is ultimately used as a component for animal feed mixtures. It is high in protein, and the constituent amino acids are used by an animal's body as building blocks for its own proteins. These proteins are, in turn, the major building blocks of the animal's muscle structures and organ tissues.
The rumen functions to digest the difficult-to-digest materials eaten by cattle. Such materials include feeds and grass fibers. The fluids and bacteria present in the rumen attack cellulose as well as proteins. The proteins comprise a high content of nitrogen, roughly 15 to 18% by weight. The rumen bacteria breaks down the protein into various products, some of which are gaseous in nature such as gaseous amines, ammonia or methane. These gaseous products are generally lost to the nutrition of the animal. Soybean meal processed according to conventional solvent extraction methods typically produces substantial quantities of gaseous products.
If untreated or raw soybeans were to be fed to a cow, the proteins present in the soybeans would be rapidly broken down in the cow's rumen, a component of a cow's digestive system. The protein, in its untreated form, is highly soluble and readily breaks down in the rumen fluids. The protein diffuses through the membrane wall of the bacteria which converts it to amines, methane and ammonia. This permits the bacteria to maintain its own life and allows it to produce energy for its own multiplication. Relatively little protein is able to pass through the rumen and into the abomasum, the second part of the digestive system of the ruminant animal.
It is desirable to develop a protein which can significantly bypass the rumen and move into the abomasum which bleeds the protein to the small intestine, the third and final part of the ruminant animal's digestive system. From there, the amino acids are put into the bloodstream and resynthesized into constituents such as muscle tissue or milk protein.
In view of the highly soluble nature of soybean proteins or any other feed proteins, their conversion for use by the animal body is generally not efficient. That is, an excess of soybean proteins is needed to produce a given quantity of animal protein, whether in the form of animal tissue, protein in milk, or both. The efficiency of the conversion process depends upon numerous factors including species, age and condition of the animal, as well as the properties of the feed itself.
The proteins used in dairy nutrition are composed of amino acids, several of which are considered essential amino acids. Essential amino acids are those amino acids which the animal body is unable to synthesize itself and, therefore, must be supplied from an extraneous source, i.e., the feed. Typical examples of essential amino acids required by cows and cattle include lysine and methionine. Absorption of essential amino acids by the animal body is vital for muscle maintenance, muscle growth, reproduction and, in the case of dairy cattle, lactation.
There are two sources of essential amino acids in the ingested feed. First, there is the microbial protein produced in rumen fermentation by microorganisms in the rumen, the largest compartment of the multi-compartment stomach of the cow. The second source is the dietary protein that escapes (or bypasses) rumen fermentation ("bypass protein").
As a cow's milk production increases, the protein produced in rumen fermentation is unable to supply all the amino acids necessary for maximum growth or milk production of dairy cattle. A substantial portion of amino acids is derived from protein which bypasses the rumen and passes into the small intestine where digestion and absorption of these amino acids occur. Since this partitioning of the amino acid absorption increases the overall utilization of the protein in the feed, it may be stated that protein efficiency is increased when protein escapes fermentation in the rumen.
The cost of feeding dairy cattle is primarily determined by the cost of protein. Thus, by improving protein efficiency, less protein is needed for a given production of animal protein, whether in the form of maintenance, growth or production of milk. The cost of feeding is thereby reduced.
A maximization of lactation performance (i.e., milk production) in dairy cows calls for formulating feed rations to contain optimum levels of bypass or escape protein, utilizing high quality protein sources.
The term "protein quality" is used to describe the amino acid balance of the protein relevant to feeding a specific animal. A high quality protein is one that supplies a high level of essential amino acids in the proportions and amounts needed by a specific cow. Soybean meal is considered to be a high quality protein for feeding dairy cattle.
Soybeans may be fed to dairy cattle in several distinctive forms. Each distinctive from has its own particular usefulness as a dairy feed supplement.
Raw soybeans are the commodity harvested on the farm and subsequently dried for storage and/or further processing. This commodity typically contains 70% solids, 18-20% oil and 10-12% moisture.
In preparing soybean meal from raw soybean, a number of processes or methods are known in the art. Conventional soybean meal is available in a variety of forms or types prepared according to various methods.
One form of conventional soybean meal comprises full fat soybean meal. This is a meal prepared by grinding soybeans without any removal of the lipid component of the soybean.
A second type of conventional soybean meal is solvent soybean meal. This is a meal produced by solvent extraction of soybeans. It comprises 1% or less residual oil. By far, the largest quantity of soybean meal available in the marketplace is of this origin.
A third form of conventional soybean meal is expeller soybean meal. This is a meal prepared by conditioning comminuted soybeans and subsequently mechanically extracting a substantial part of the oil content of the beans. Mechanical extraction is best performed using a screw press, i.e., a piece of equipment generally referred to as an expeller (hence the appellation "expeller" soybean meal). This meal generally contains 4 to 8% residual oil on a bone-dry basis (i.e., when samples are dried first to a low (generally less than 0.2%) moisture content).
The bypass protein value of full fat soybean meal is relatively low, approximately 35% based on current analysis. However, only limited quantities of full fat soybeans can be added to feed rations, due to the fact that the high oil content may be a causative factor in some digestive disturbances. Too large a quantity of fat in feed upsets the rumen bacteria, and much of the protein in the feed is not converted to animal muscle or milk. Similarly, the bypass protein value of solvent soybean meal is low, i.e., about 35%.
Production of expeller soybean meal is limited and, based upon samples measured from various small production sources in the United States, its quality in terms of bypass value and residual oil content is quite variable.
There are other disadvantages to the production of expeller soybean meal. For instance, during the process, seeds are comminuted and heated to remove moisture and partially insolubilize protein. The oil is then pressed out at relatively high temperatures, about 200-210.degree. F. This temperature provides a problem with pressing and produces a poorer quality oil. Though the expeller meal protein is partially insolubilized, its bypass value is relatively low.
Table I below shows typical bypass protein levels of selected soybean products:
TABLE I* ______________________________________ Soybean Product Protein % Bypass ______________________________________ Extruded meal, full-fat meal 35 Whole soybeans 26 Soybean meal, solvent extracted 35 Soybean meal, unheated 14 Soybean meal, dried at 120.degree. C. (248.degree. F.) 59 ______________________________________ *Extracted from TABLE 111, Bypass Protein (percent of undegraded protein) in common feeds, Feeds & Nutrition, Ensminger et al., 1990 and National Research Council, Report on Nutrient Requirements of Dairy Cattle, 6th Edition, 1988.
As stated earlier, a further measure of protein quality is the availability of the essential amino acids lysine and methionine. Since the known techniques for increasing protein bypass value generally involve the application of heat and/or chemicals to the soybean proteins, these conventional processes show damage to the heat labile amino acids. They are broken down so as not to be useful to the animal, and are known in the art as having a reduced availability of essential amino acids. Also, the resulting feed often becomes unpalatable.
There is a need and desire to develop a method for treating soybeans such that the resulting meal is undamaged and has an improved protein bypass value. Such a method would produce a feed offering increased lactation in dairy cows and improved muscle structure in cattle. Such a method should further produce a soybean meal having low protein degradability in the rumen, hence a high rumen bypass value. Such a method should be economical and should provide a resulting cost effective feed.
The prior art consists of many techniques in which heat is applied to soybean proteins in the presence of chemicals to produce products with high bypass values. Many of the products described in the prior art are not commercially available and have not been commercially successful because of high cost of production, palatability problems, reduced availability of essential amino acids, and the like.
The present invention contemplates a new and improved method for preparing a high quality bypass protein product with a high availability of essential amino acids from soybean proteins.